U.S. patent number 6,411,190 [Application Number 09/631,647] was granted by the patent office on 2002-06-25 for circuit breaker.
This patent grant is currently assigned to Yazaki Corporation. Invention is credited to Takashi Gohara, Yoshinori Ikuta, Mitsuaki Morimoto, Hideo Takahashi, Yasuhiro Tamai, Noboru Yamaguchi.
United States Patent |
6,411,190 |
Yamaguchi , et al. |
June 25, 2002 |
Circuit breaker
Abstract
A current sensor 73 detects a current flowing through a first
buss bar 11. When a current value detected by the current sensor 73
became equal to or greater than a threshold current value, a CPU 74
outputs a driving control signal to a driving circuit 77, and the
driving circuit 77 operates an, ignitor 29 through a second
substrate 65 and a terminal 50. Therefore, the ignitor 29 ignites,
a second projection 41 is melted by heat of a heating agent 27, a
compression spring 34 is expanded and a thermite case 26 jumps up.
Thus, electrical connection between the thermite case 26 and the
first and second buss bars 11, 19 is interrupted. Further, since an
outer container 61 in which the current sensor 73, the CPU and the
driving circuit 77 are accommodated is integrally assembled with
the cap 14a and the resin case 14b in which the thermite case 26,
the ignitor 29, the compression spring 34 and the second projection
41 are accommodated, non-operational state of the ignitor 29 due to
disconnection of electric wire is not generated.
Inventors: |
Yamaguchi; Noboru
(Shizuoka-ken, JP), Gohara; Takashi (Shizuoka-ken,
JP), Tamai; Yasuhiro (Shizuoka-ken, JP),
Takahashi; Hideo (Shizuoka-ken, JP), Morimoto;
Mitsuaki (Shizuoka-ken, JP), Ikuta; Yoshinori
(Shizuoka-ken, JP) |
Assignee: |
Yazaki Corporation (Tokyo,
JP)
|
Family
ID: |
16749623 |
Appl.
No.: |
09/631,647 |
Filed: |
August 2, 2000 |
Foreign Application Priority Data
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Aug 3, 1999 [JP] |
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11-220340 |
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Current U.S.
Class: |
337/401; 180/279;
200/61.08; 307/10.1; 307/10.7; 337/157; 337/405; 337/408;
361/115 |
Current CPC
Class: |
H01H
39/00 (20130101); H01H 2039/008 (20130101) |
Current International
Class: |
H01H
39/00 (20060101); H01H 071/20 (); H01H 037/76 ();
B60L 001/00 (); B60K 028/10 () |
Field of
Search: |
;337/401,157,404-406,408,409 ;307/119,9.1-10.8
;180/271,274,279,281-283 ;200/61.08 ;361/115 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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S64-29756 |
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Feb 1989 |
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JP |
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10-55742 |
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Feb 1998 |
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JP |
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10-241523 |
|
Sep 1998 |
|
JP |
|
10-324207 |
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Dec 1998 |
|
JP |
|
Primary Examiner: Vortman; Anatoly
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
Claims
What is claimed is:
1. A circuit breaker comprising
a conductive heating portion disposed between a first connecting
terminal and a second connecting terminal such that the heating
portion is in contact with the first connecting terminal and the
second connecting terminal and having a heating agent therein,
an ignitor accommodated in the heating portion for igniting the
heating agent charged in the heating portion when abnormal
conditions of a vehicle are encountered,
an expandable resilient member which is disposed such that the
resilient member is in contact with the heating portion for pushing
the heating portion,
a melting member for maintaining the resilient member in its
compressed state,
a first container for accommodating the heating portion, the
ignitor, the resilient member and the melting member,
a detecting portion for detecting an abnormality of the
vehicle,
a judging portion for judging whether the vehicle is under abnormal
conditions based on an output from the detecting portion and for
outputting a driving control signal when the judging portion judged
that the vehicle is under the abnormal conditions,
a driving portion for operating the ignitor based on the driving
control signal from the judging portion, and
a second container for accommodating the detecting portion, the
judging portion and the driving portion, and the second container
being integrally assembled with the first container.
2. A circuit breaker according to claim 1, further comprising
a connector having a terminator whose one end is electrically
connected to the ignitor, and
a substrate provided for mounting the detecting portion, the
judging portion and the driving portion into the second container,
wherein
the other end of the terminal is soldered to the substrate, and the
driving portion and the ignitor are electrically connected to each
other through the substrate and the terminal.
3. A circuit breaker according to claim 2, wherein the connector is
detachable with respect to the ignitor, and the connector is
disengaged from the ignitor when the ignitor is moved by ignition
of the heating agent.
4. A circuit breaker according to claim 1, wherein
the detecting portion is a current sensor for detecting a current
flowing through at least one of the first connecting terminal and
the second connecting terminal, and
the judging portion judges whether a current value detected by the
current sensor became equal to or greater than a preset threshold
value, and if the current value detected by the current sensor
became equal to or greater than the threshold value, the judging
portion outputs the driving control signal to the driving
portion.
5. A circuit breaker according to claim 1, wherein
the melting member is made of resin member which is formed in the
first container and which prevents a pushing force of the resilient
member against the heating portion.
6. A circuit breaker according to claim 1, wherein
an end of the heating portion is formed with a side wall, and the
side wall is connected to the first connecting terminal and the
second connecting terminal through a low-melting material.
Description
BACKGROUND OF THE INVENTION
1. Field of The Invention
The present invention relates to a circuit breaker for interrupting
an electric circuit for a short time, and more particularly, to a
circuit breaker integrally provided with a breaker portion for
interrupting an electric circuit and a control portion for
controlling the breaker portion.
2. Description of The Related Art
In an electrical component system provided in a vehicle, when
something is wrong with a load of a power window or the like, or
when something is wrong with a wire harness or the like constituted
by a plurality of electric wires connecting a battery and various
loads to each other, a high-current fuse inserted between the
battery and the wire harness is blown out to interrupt a connection
between the battery and the wire harness, thereby preventing the
loads, the wire harness and the like from being burnt and
damaged.
However, in the case of the electric component system using such a
high-current fuse, even if something is wrong with the load of the
power window or the like, or something is wrong with the wire
harness or the like connecting the battery and various loads, the
fuse is not blown out unless a current equal to or greater than a
tolerated value which is previously set for the high-current fuse.
Therefore, various protecting apparatuses have been developed for
detecting the current and interrupt the connection between the
battery and the wire harness when a high current close to the
tolerated value is continuously flowing.
FIG. 1 is a sectional view showing one example of the protecting
apparatus using a bimetal (Japanese Utility Model Application
Laid-open No. S64-29756). The protecting apparatus shown in FIG. 1
is made of insulation resin, and comprises a housing 103 formed at
its upper portion with a fuse accommodating portion 102, a lid 113
for closing the fuse accommodating portion 102 such that the latter
can be opened and closed, a power source terminal 105 disposed in a
lower portion in the housing 103 such that an upper end of the
power source terminal 105 projects into the fuse accommodating
portion 102 and a lower end thereof is exposed outside, and the
exposed portion of the power source terminal 105 being connected to
a positive terminal of a battery 104, a load terminal 109 disposed
in a lower portion in the housing 103 such that an upper end of the
load terminal 109 projects into the fuse accommodating portion 102
and a lower end thereof is exposed outside, and the exposed portion
of the load terminal 109 being connected to a load 108 through an
electric wire 107 constituting a wire harness 106, a fusible member
110 made of low-melting metal disposed in the fuse accommodating
portion 102, and having one end connected to an upper end of the
power source terminal 105 and the other end connected to an upper
end of the load terminal 109, an intermediate terminal 111 disposed
in a lower portion in the housing 103 such that the intermediate
terminal 111 is located at an intermediate position between the
power source terminal 105 and the load terminal 109 and a lower end
of the intermediate terminal 111 is exposed outside, and the
exposed portion being connected to a negative terminal of the
battery 104, and a bimetal 112 which is made of a long plate-like
member comprising two kinds of metal bonded together and which is
disposed such as to be opposed to the fusible member 110 such that
a lower end of the bimetal 112 is connected to an upper end of the
intermediate terminal 111 and an upper end thereof being bent into
an L-shape.
When an ignitor switch and the like of the vehicle are operated,
and a current is flowing through a path comprising the positive
terminal of the battery 104, the power source terminal 105, the
fusible member 110, the load terminal 109, the electric wire 107 of
the wire harness 106, the load 108, and the negative terminal of
the battery 104, and when an abnormal condition occurs in the load
108 or in the wire harness 106 connecting the load 108 and a
protecting apparatus 101, and a current equal to or greater than
the tolerated value flows through the fusible member 110, the
fusible member 110 is heated and blown out for protecting the load
108, the wire harness 106 and the like.
Further, even if something is wrong with the load 108 or the wire
harness 106 connecting the load 108 and the protecting apparatus
101, and a large current flows through the fusible member 110, if
the current does not exceed the tolerated value, the fusible member
110 is heated by the current following through the latter, and the
bimetal 112 starts deforming. When a predetermined time is elapsed
from the instant when the large current starts flowing through the
fusible member 110, a tip end of the bimetal 112 comes into contact
with the fusible member 110, and a large short-circuit current
flows through the fusible member 110 in a path comprising the
positive terminal of the battery 104, the power source terminal
105, the fusible member 110, the intermediate terminal 111, and the
negative terminal of the battery 104, and the latter is blown
out.
With the above structure, even when a current equal to or lower
than the tolerated value flows for a preset time or longer, the
circuit is interrupted to protect the wire harness 106 and the load
108.
As another protecting apparatus investigated by the present
inventors rather than this protecting apparatus 101, a protecting
apparatus 121 shown in FIG. 2 has been also developed (Japanese
Utility Model Application Laid-open No. S64-29756).
The protecting apparatus 121 shown in FIG. 2 comprises a housing
122 made of insulation resin, a power source terminal 124 embedded
in one side surface of the housing 122 and having a lower end
connected to a positive terminal of a battery 123, and a load
terminal 128 embedded in the other side surface of the housing 122
and having a lower end connected to a load 127 through an electric
wire 126 constituting a wire harness 125. The protecting apparatus
121 further comprises an electric wire 131 including a fusible lead
129 which is made of low-melting metal and formed into U-shape and
a heat-proof coating 130 formed such as to cover the fusible lead
129. The protecting apparatus 121 further comprises a coil 132. The
coil 132 is made of shape-memory alloy which is formed into a shape
wound around the electric wire 131 as shown in FIG. 2 when it is in
a martensite phase state, and which is returned to its original
phase shape fastening the electric wire 131 when it is heated from
120.degree. C. to 170.degree. C. The protecting apparatus 121
further comprises an external terminal 133 whose upper end is
connected to one end of the coil 132 and whose lower end is
connected to a negative terminal of the battery 123.
When an ignitor switch and the like of the vehicle are operated,
and a current is flowing through a path comprising the positive
terminal of the battery 123, the power source terminal 124, the
fusible lead 129 of the electric wire 131, the load terminal 128,
the electric wire 126 of the wire harness 125, the load 127 and the
negative terminal of the battery 123, and when an abnormal
condition occurs in the load 127 or in the wire harness 125
connecting the load 127 and a protecting apparatus 121, and a
current equal to or greater than the tolerated value flows through
the fusible lead 129, the fusible lead 129 is heated and blown out
for protecting the load 127, the wire harness 125 and the like.
Further, even if something is wrong with the load 127 or the wire
harness 125 connecting the load 127 and the protecting apparatus
121, and a large current flows through the fusible lead 129, if the
current does not exceed the tolerated value, the fusible lead 129
is heated by the current flowing through the latter, and a
temperature of the coil 132 rises. When a predetermined time is
elapsed from the instant when the large current starts flowing
through the fusible lead 129, and the temperature of the coil 132
rises to 120.degree. C. to 170.degree. C., the coil 132 changes
from its martensite phase state to its original phase and bites
into the heat-proof coating 130 which is softened by heat and comes
into contact with the fusible lead 129, and a large short-circuit
current flows through the fusible lead 129 in a path comprising the
positive terminal of the battery 123, the power source terminal
124, the fusible lead 129, the coil 132, the external terminal 133,
and the negative terminal of the battery 123, and the latter is
blown out.
With the above structure, even when a current equal to or lower
than the tolerated value flows for a preset time or longer, the
circuit is interrupted to protect the wire harness 125 and the load
127.
However, in the above-described conventional protecting apparatuses
101 and 121, there are problems as follows.
First, in the case of the protecting apparatus shown in FIG. 1, it
is detected whether a large current flows through the fusible
member 110 using the bimetal 112 made of two kinds of metals having
different thermal expansion coefficients and bonded to each other.
Therefore, if the magnitude of the current is flowing through the
fusible member 110, the bimetal 112 is deformed, and the time that
elapsed before the circuit is interrupted is varied, depending on
the current flowing therethrough.
Thus, when a failure that a large current flows intermittently
occurs, a temperature of the fusible member 110 does not rise more
than a certain value, and there is an adverse possibility that the
wire harness 106 or the load 108 may be burnt before the protecting
apparatus 101 interrupts the circuit.
In the case of the protecting apparatus 121 shown in FIG. 2, it is
detected whether a large current flows through the fusible lead 129
using the coil 132 made of shape-memory alloy. Therefore, if the
magnitude of the current is flowing through the fusible lead 129,
the coil 132 is deformed, and the time that elapsed before the
circuit is interrupted is varied--depending upon the flowing
current.
Thus, when a failure that a large current flows intermittently
occurs, a temperature of the fusible lead 129 does not rise more
than a certain value, and there is an adverse possibility that the
wire harness 125 or the load 127 may be heated excessively before
the protecting apparatus 121 interrupts the circuit. Further, if
the bimetal or shape-memory alloy is used, since the
deformation-starting temperature is usually as low as about
100.degree. C., it is difficult to use it at 120.degree. C. to
125.degree. C. which is the using environment temperature condition
of the vehicle.
Further, in the protecting apparatuses shown in FIGS. 1 and 2, the
heat reaction time of the bimetal 112 or of the coil 132 which is a
thermal-deformable electrical conduction member is varied depending
upon the current flowing therethrough. Further, the heat reaction
of the thermal-deformable electrical conduction member is not
operated timely in some cases when an abnormal condition occurs
(when excessive current flows).
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a circuit
breaker capable of reliably interrupting a circuit in a short time
to protect an electrical part when an abnormal signal of a vehicle
is inputed.
To achieve the above object, according to a first aspect of the
present invention, there is provided a circuit breaker comprising a
conductive heating portion disposed between a first connecting
terminal and a second connecting terminal such that the heating
portion is in contact with the first connecting terminal and the
second connecting terminal and having a heating agent therein, an
ignitor accommodated in the heating portion for igniting the
heating agent charged in the heating portion when abnormal
conditions of a vehicle are encountered, an expandable resilient
member which is disposed such that the resilient member is in
contact with the heating portion for pushing the heating portion, a
melting member for maintaining the resilient member in its
compressed state, a first container for accommodating the heating
portion, the ignitor, the resilient member and the melting member,
a detecting portion for detecting an abnormality of the vehicle, a
judging portion for judging whether the vehicle is under abnormal
conditions based on an output from the detecting portion and for
outputting a driving control signal when the judging portion judged
that the vehicle is under the abnormal conditions, a driving
portion for operating the ignitor based on the driving control
signal from the judging portion, and a second container for
accommodating the detecting portion, the judging portion and the
driving portion, and the second container being integrally
assembled with the first container.
According to the first aspect, if the detecting portion detects an
abnormality of the vehicle, the judging portion judges whether the
vehicle is under the abnormal conditions based on the output from
the detecting portion, and if the judging portion judged that the
vehicle is under the abnormal conditions, the judging means output
the driving control signal, and the driving portion operates the
ignitor based on the driving control signal from the judging
portion. Therefore, the ignitor ignites the heating agent charged
in the heating portion, the melting member is melted by the heat of
the heating agent, the compressed resilient member is expanded and
the heating portion jumps up. Therefore, the electrical connection
between the heating portion and the first and second connecting
terminals is cut off, and the circuit can be interrupted.
Accordingly, since the second container accommodating the detecting
portion, the judging portion and the driving portion, and the
second container being integrally assembled with the first
container accommodating the heating portion, the ignitor, the
resilient member and the melting member, a non-operational state of
the ignitor due to disconnection of electric wire is
eliminated.
According to a second aspect of the invention, in the circuit
breaker of the first aspect, the circuit breaker further comprises
a connector having a terminator whose one end is electrically
connected to the ignitor, and a substrate provided for mounting the
detecting portion, the judging portion and the driving portion into
the second container, and the other end of the terminal is soldered
to the substrate, and the driving portion and the ignitor are
electrically connected to each other through the substrate and the
terminal.
According to the second aspect, the one end of the terminal of the
connector is electrically connected to the ignitor, the other end
of the terminal is soldered to the substrate on which the driving
portion is mounted, and the driving portion and the ignitor are
electrically connected to each other through the substrate and the
terminal. Therefore, there is no connection using electric wire and
thus, an adverse possibility that the ignitor 29 is erroneously
operated due to noise is reduced.
According to a third aspect of the invention, in the circuit
breaker of the second aspect, the connector is detachable with
respect to the ignitor, and the connector is disengaged from the
ignitor when the ignitor is moved by ignition of the heating
agent.
According to the third aspect, when the ignitor is pushed upward
and moved by ignition of the heating agent, the connector is
disengaged from the ignitor, and the power supply to the ignitor
can be automatically stopped. With this structure, the current does
not keep flowing, heat is not transmitted to the substrate and the
like and thus, the electronic such as the substrate and device is
less prone to be damaged.
According to a fourth aspect of the invention, in the circuit
breaker of the first aspect, the detecting portion is a current
sensor for detecting a current flowing through at least one of the
first connecting terminal and the second connecting terminal, and
the judging portion judges whether a current value detected by the
current sensor became equal to or greater than a preset threshold
value, and if the current value detected by the current sensor
became equal to or greater than the threshold value, the judging
portion outputs the driving control signal to the driving
portion.
According to a fifth aspect of the invention, in the circuit
breaker of the first aspect, the melting member is made of resin
member which is formed in the first container and which prevents a
pushing force of the resilient member against the heating
portion.
According to the fifth aspect, since the melting member formed in
the first container is made of resin member which prevents a
pushing force of the resilient member against the heating portion,
the resin member can be melted and the heating portion and the
ignitor can be lifted up when the heating agent is ignited.
According to a sixth aspect of the invention, in the circuit
breaker of the first aspect, an end of the heating portion is
formed with a side wall, and the side wall is connected to the
first connecting terminal and the second connecting terminal
through a low-melting material.
According to the sixth aspect, since the side wall is connected to
the first connecting terminal and the second connecting terminal
through the low-melting material, if the resin member and the
low-melting material are melted by the heat of the heating agent,
the heating portion jumps up, the electrical connection between the
first and second connecting terminals is cut off and therefore, the
circuit can reliably be interrupted within a short time to protect
an electric part. Further, since the spring force is not applied to
the low-melting metal which connects the first and second
connecting terminals and the heating portion, it is possible to
enhance the reliability of the connected portion.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view showing one example of a conventional
protecting apparatus using a bimetal;
FIG. 2 is a sectional view showing another example of the
conventional protecting apparatus;
FIG. 3 is a sectional view of a circuit breaker of an embodiment
taken along the line III--III in FIG. 4;
FIG. 4 is a top view of the circuit breaker of the embodiment;
FIG. 5 is a sectional view of the circuit breaker of the embodiment
taken along the line V--V in FIG. 4; and
FIG. 6 is a block diagram of the circuit breaker of the
embodiment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
An embodiment of a circuit breaker of the present invention will be
explained in detail with reference to the drawings.
The circuit breaker of the present embodiment is characterized in
that a circuit from a battery to a load can be reliably interrupted
within a short time when something is wrong with a vehicle, and the
circuit breaker integrally provided with a breaker portion for
interrupting the circuit and a control portion for controlling the
breaker portion.
In the circuit breaker shown in FIG. 3, a plate-like long first bus
bar 11 is made of copper or copper alloy for example, and is formed
with a round hole 12 connected to a battery or the like. The first
bus bar 11 is bent downward substantially at the right angle.
A plate-like long second bus bar 19 is also made of copper or
copper alloy for example, and is formed with a round hole 20
connected to a load or the like. The second bus bar 19 is also bent
downward substantially at the right angle.
A gap 14a and a resin case 14b are disposed between the first bus
bar 11 and the second bus bar 19. The gap 14a and the resin case
14b constitute a first container made of insulating material such
as resin (thermoplastic resin).
A thermite case 26 made of copper, copper alloy or the like is
accommodated in the resin case 14b, and a heating agent 27 is
charged in the thermite case 26, and an ignitor 29 is accommodated
in the thermite case 26.
The ignitor 29 includes an igniting agent which is ignited by heat
generated by current flowing through a terminal 50 of a connector
45 when something is wrong with the vehicle, thereby allowing the
heating agent 27 to generate a thermite reaction heat.
A left side wall formed on the thermite case 26 is connected to a
bus bar tip end 13 through low-melting metal 23 as low-melting
material such as solder (melting point is 200.degree. C. to
300.degree. C.) or the like. A right side wall formed on the
thermite case 26 is connected to a bus bar tip end 21 through
low-melting metal 23. Therefore, the first bus bar 11 and the
second bus bar 19 can be electrically connected to each other
through the low-melting metal 23 and the thermite case 26.
The low-melting metal 23 is made of at least one metal selected
from Sn, Pb, Zn, Al and Cu.
The heating agent 27 is made of metal-oxide powder such as ferric
oxide (Fe.sub.2 O.sub.3) and aluminum powder, and is thermite agent
which thermite-reacts by heat of the lead wire 31 to generate high
heat. Chromic oxide (Cr.sub.2 O.sub.3), manganese oxide (MnO.sub.2)
or the like may be used instead of ferric oxide (Fe.sub.2
O.sub.3).
The heating agent 27 may be made of mixture comprising at least one
metal powder selected from B, Sn, Fe, Si, Zr, Ti and Al; at least
one metal selected from CuO, MnO.sub.2, Pb.sub.3 O.sub.4,
PbO.sub.2, Fe.sub.3 O.sub.4 and Fe.sub.2 O.sub.3 ; and at least one
additive comprising alumina, bentonite and talc. Such a heating
agent is easily is ignited by the ignitor 29, and the low-melting
metal 23 can be melted within a short time.
An expandable compression spring 34 is disposed as a resilient
member between the thermite case 26 and the resin case 14b, and
this compression spring 34 pushes the thermite case 26 upward.
As shown in FIG. 5, the cap 14a is formed with a groove 37, and a
first projection 39 formed on the resin case 14b is engaged with
the groove 37. The resin case 14b is formed with a second
projection 41 made of resin which is melted by heat. The second
projection 41 pushes an upper face of the thermite case 26 to
prevent the thermite case 26 from moving upward by a spring force
of the compression spring 34.
A connector 45 having a terminal 50 is detachably mounted to the
ignitor 29. One end of the terminal 50 is connected to a heater
(not shown) provided on the ignitor 29, and the other end of the
terminal 50 is soldered to a second substrate 65. With this
structure, the current from the second substrate 65 flows into the
heater through the terminal 50, and the ignitor 29 is operated by
heat generated by the heater.
A pair of L-shaped and inverted L-shaped container-assembling ribs
62 are formed on the resin case 14b. An outer container 61 as a
second container is assembled to the resin case 14b through the
pair of container-assembling ribs 62.
This outer container 61 accommodates a first substrate 63 disposed
substantially in parallel to the left side wall of the resin case
14b, and a second substrate 65 disposed substantially vertically
with respect to the first substrate 63 such that the second
substrate 65 is opposed to a bottom face of the resin case 14b. The
first substrate 63 is assembled to a substrate-assembling portion
64 which is formed in the outer container 61, and comprises a
current sensor 73, a central processing unit (CPU) 74, a driving
circuit 77 and the like. The current sensor 73 comprises a
magnetoelectric converting element and the like disposed in the
vicinity of the first bus bar 11 for detecting a current flowing to
the first bus bar 11.
The outer container 61 is formed with projections 67 and 68, and
the second substrate 65 is screwed to the projection 68 by a screw
69 and fixed to the outer container 61. The second substrate 65 is
electrically connected to the first substrate 63 through a jumper
wire 66, and the other end of the terminal 50 of the connector 45
is soldered to the second substrate 65. With this structure, a
current is supplied from the driving circuit 77 of the first
substrate 63 to the ignitor 29 through the second substrate 65 and
the terminal 50.
Next, details of the circuit structure in the outer container
provided in the circuit breaker will be explained with reference to
FIG. 6. As shown in FIG. 6, the circuit breaker is provided between
the battery 1 and the load 5, and comprises a power source 70
having a voltage sensor 71 for detecting a voltage from the battery
1, a sensor 72 having a current sensor 73 and a temperature sensor
74, a judging portion 75, the driving circuit 77, a heater 79, the
igniting agent 82 which is ignited by heat of the heater 79, the
first bus bar 11 and the second bus bar 19.
The power source 70, the sensor 72, the judging portion 75 and the
driving circuit 77 are provided in the outer container 61. The
heater 79, the igniting agent 82, the first bus bar 11 and the
second bus bar 19 are provided in the resin case 14b.
The power source 70 is of 5V for example, opposite end voltages of
the battery 1 are input to the power source 70, and the power
source 70 supplies voltage to the sensor 72, the judging portion 75
and the driving circuit 77. The current sensor 73 detects a current
flowing through the load 5, and is a Hall device or the like for
converting a magnetic field generated by the current into an
electric signal. The temperature sensor 74 is a thermistor for
example for detecting a temperature by resistance varied by heat
generated by the current.
The judging portion 75 comprises the CPU 74, and judges whether a
current value detected by the current sensor 73 becomes equal to or
greater than a threshold current value. The driving circuit 77
includes a field-effect transistor (FET) or the like for example,
and turns the heater 79 ON to allow a current to flow when the
judging portion 75 judges that the current value detected by the
current sensor 73 becomes equal to or greater than the threshold
current value.
The judging portion 75 may turn the FET ON to allow a current to
flow to the heater 79 when a temperature value detected by the
temperature sensor 74 becomes equal to or greater than a threshold
temperature, or may turn the FET ON to allow a current to flow to
the heater 79 when a voltage value detected by the voltage sensor
71 becomes abnormal voltage value.
The igniting agent 82 is ignited by the heat of the heater 79 to
interrupt the electrical connection between the first bus bar 11
and the second bus bar 19 to cut off the power source supply from
the battery 1 to the load 5.
Next, the operation of the circuit breaker of the present
embodiment structured as described above will be explained with
reference to the drawings.
First, under the normal condition, the first bus bar 11 and the
second bus bar 19 are electrically connected to each other through
the low-melting metal 23 and the thermite case 26, and a current is
supplied to the load (not shown) from the battery (not shown).
Next, if the current sensor 73 provided in the outer container 61
detects a current flowing through the first bus bar 11, the judging
portion 75 judges whether the current value detected by the current
sensor 73 became equal to or greater than a preset threshold
current value.
If the detected current value became equal to or greater than the
threshold current value, the driving circuit 77 provided on the
first substrate 63 allows a current to flow to the heater 79 of the
ignitor 29 through the second substrate 65 and the terminal 50.
Then, the ignitor 29 is ignited by heat generated by the current
and therefore, the heating agent 27 which is a thermite agent
generates a thermite reaction heat according to the following
reaction expression:
The thermite case 26 is heated by the thermite reaction heat, the
low-melting metals 23 connecting the bus bar tip end 13 and the
left side wall of the thermite case 26 to each other, as well as
the low-melting metal 23 connecting the bus bar tip end 21 and the
right side wall of the thermite case 26 are heated and melted by
heat of the heating agent 27 and the thermite case 26.
Simultaneously with this, the second projection 41 made of resin
member formed on the resin case 14b is melted by the heat.
As a result, the compression spring 34 which had been compressed is
expanded, and the thermite case 26 accommodating the ignitor 29
jumps upward (26' in FIG. 3 represents the thermite case after it
moved upward).
Therefore, the electrical connection between the thermite case 26,
the first bus bar 11 and the second bus bar 19 is cut off. That is,
the first bus bar 11 and the second bus bar 19 are electrically
interrupted, and the electric circuit of the vehicle is
interrupted.
When the ignitor 29 and the thermite case 26 jumped up, the
connector 45 is disengaged from the ignitor 29.
As described above, according to the circuit breaker of the present
embodiment, it is possible to reliably interrupt the electric
circuit of a vehicle within a short time to protect an electrical
part.
Further, since the outer container 61 in which the current sensor
73, the judging portion 75 and the driving circuit 77 are
accommodated is integrally assembled with the cap 14a and the resin
case 14b in which the thermite case 26, the ignitor 29, the
compression spring 34 and the second projection 41 are
accommodated, non-operational state of the ignitor 29 due to
disconnection of electric wire from the driving circuit 77 is not
generated.
Further, the one end of the terminal 50 is electrically connected
to the ignitor 29, the other end of the terminal 50 is soldered to
the second substrate 65 and the driving circuit 77 and the ignitor
29 are electrically connected to each other through the second
substrate 65 and the terminal 50. Therefore, there is no connection
using electric wire and thus, an adverse possibility that the
ignitor 29 is erroneously operated due to noise is reduced.
Even if the number of circuit protecting portions is varied, it is
possible to deal with a plurality of circuit protecting portions by
commonly using the control portion without changing the control
portion such as the current sensor 73, the judging portion 75 and
the driving circuit 77 included in the outer container 61. Further,
the breaker portion and the controlling portion are integrally
formed, it is possible to simplify the wire harness and the
connector constituting peripheral circuits of the circuit
breaker.
Further, since the second projection 41 formed in the resin case
14b prevents the compression spring 34 from expanding upward, the
spring force is not applied to the low-melting metal 23 which
connects the first bus bar 11, the second bus bar 19 and the
thermite case 26 and thus, it is possible to enhance the
reliability of the connected portion.
Furthermore, since the ignitor 29 is disengaged from the connector
45 and lifted up after ignitor, power supply to the ignitor 29 can
automatically stopped. With this structure, the current does not
keep flowing, heat is not transmitted to the substrate and the like
and thus, the electronic such as the substrate and device is less
prone to be damaged.
Further, since the cap 14a is put on the resin case 14b, the
thermite case 26 will not jump out from the cap 14a when the
circuit is interrupted, and this can prevent a burn caused by
heat.
The, present invention is not limited to the circuit breaker of the
above-described embodiment. Although the compression spring 34 and
the low-melting metal 23 are provided, and the circuit is
interrupted when the second projection 41 and the low-melting metal
23 are melted in the embodiment, only the second projection 41 may
be provided without providing the low-melting metal 23, and the
circuit may be interrupted when the second projection 41 is
melted.
In the circuit breaker of the embodiment, the second projection 41
formed on the resin case 14b pushes the upper face of the thermite
case 26, and the upward movement of the thermite case 26 by the
spring force of the compression spring 34 is prevented.
For example, the thermite case 26 may be formed with a screw this
screw may be threadedly engaged with another screw made of resin
member as a melting member formed on the resin case 14b, and the
upward movement of the thermite case 26 by the spring force of the
compression spring 34 may be prevented by fixing the thermite case
26 to the resin case 14b.
In this case, when the thermite case 26 is heated, the screw made
of resin member formed on the resin case 14b is melted, the
thermite case 26 is moved upward by the spring force of the
compression spring 34 to interrupt the circuit.
Although the second projection 41 and the screw were indicated as
the melting members, the melting members are not limited to those,
and the melting member may be a resin member or a low-melting metal
which maintains the compression spring 34 in its compressed state
under a normal condition, and which is melted by heat when a
circuit is to be interrupted. It is of course possible to make
various modifications without departing from the spirit or scope of
the invention.
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